Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-01-21
2001-07-10
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S090000, C526S279000, C526S348000, C526S351000
Reexamination Certificate
active
06258902
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for polymerizing addition polymerizable monomers, such as ethylene or propylene, or combinations of one or more olefin monomers such as combinations of ethylene with one or more C
3-8
&agr;-olefins, and optionally one or more copolymerizable dienes to produce polymers having a high degree of long chain branching (LCB) using a catalyst composition comprising a Group 3-10 metal complex and a silane or hydrocarbylsilane branching agent. The resulting polymers may be usefully employed in the preparation of solid objects and articles such as a moldings, films, sheets and foamed objects by molding, casting or the like process.
In WO 97/42234 there is disclosed a process for the preparation of polymers of vinylidene aromatic monomers having a stereoregular structure of high syndiotacticity, by the use of Group 4 metal coordination catalysts and a hydrocarbylsilane or dihydrocarbylsilane adjuvant. In
Journal of the American Chemical Society,
1995, 117, 10747-19748, the use of silanes as chain transfer agents in metallocene-mediated olefin polymerizations was described. The products formed included silyl terminated polyolefins.
In U.S. Pat. Nos. 5,272,236, 5,278,272, 5,525,695 there are disclosed certain ethylene homopolymers and ethylene/ &agr;-olefin copolymers having a LCB of at least 3 chains per 10,000 carbons and a process for their preparation wherein the reincorporation of in situ generated vinyl terminated oligomers or polymers into the growing polymer chain, especially by means of a continuous polymerization process is disclosed. Although such process is relatively efficient for preparing ethylene homopolymers and copolymers, it is not particularly efficient or possible for use for forming long chain branches in homopolymers of C
3-8
&agr;-olefins, or copolymers of mixtures of C
3-8
&agr;-olefins. In U.S. Pat. No. 5,665,800 the above process was utilized to prepare EPDM compolymers having melt flow ratio, I10/I2 greater than 5.63, a molecular weight distribution, Mw/Mn, defined by the equation: Mw/Mn <(I10/I2)-4.63, and a critical shear stress at onset of gross melt fracture of greater than about 4×10
6
dynes/cm
2
. Generally increased long chain branching content is desired in olefin polymers due to improved melt rhelogy of the resulting polymer.
In U.S. Pat. No. 5,444,145, copolymers of ethylene and a branched olefin monomer are disclosed. Disadvantageously, the preparation of such copolymers by the use of the foregoing technique requires the use of a relatively expensive olefin, containing the desired preformed branched structure. Such a process is relatively inflexible and unsuited for commercial use. A process for forming long chain branched &agr;-olefin copolymer products which may utilize normal, e.g. unbranched olefin monomers is still desired in the industry. For the teachings contained therein, the foregoing patents, publications and equivalent United States patent applications are hereby incorporated by reference.
SUMMARY OF THE INVENTION
According to the present invention there is now provided a process for preparing homopolymers and copolymers of addition polymerizable monomers, or mixtures of such monomers, the process comprising contacting said monomer or mixture under high monomer conversion polymerization conditions with a catalyst composition comprising:
a) a catalyst system comprising a Group 3-10 metal complex; and
c) a silane compound corresponding to the formula:
J
j
SiH
4−j
or A
n
J
j
SiH
4-(n+j)
wherein:
J is C
1-40
hydrocarbyl,
A is a C
2-20
alkenyl group,
n is 1 or 2, and
j is 0 or 1;
wherein the polymer comprises from 0.1 to 100 long chain branches per 10,000 carbons, at least some of which comprise a silane branching center.
Compared to a polymerization process utilizing a similar catalyst composition that lacks the aforementioned silane branching agents, the present process achieves a significantly improved efficiency in long chain branch generation. In addition, the present process may be utilized in the polymerization of monomers that are not amenable to reincorporation of the products of &bgr;-hydride elimination, thereby allowing preparation for the first time of polymers containing long chain branching from such monomers. Because of the multiple reactive sites contained in the alkenyl substituted silane the quantity of the silane necessary to achieve the desired branching is small and depending on polymerization conditions rarely exceeds 5 weight percent of the reaction mixture. Use of excess alkenyl- substituted silane can result in the formation of a cross-linked polymer.
All reference to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc., 1995. Also, any reference to a Group or Series shall be to the Group or Series as reflected in this Periodic Table of the Elements, utilizing the IUPAC system for numbering groups.
Preferred silane or hydrocarbylsilane branching agents used herein include SiH
4
, methylsilane, ethylsilane, n-butylsilane, octadecylsilane, phenylsilane and benzylsilane. Mixtures of the foregoing silanes may also be used. While SiH
4
is a gas and is readily added to modern polymerization processes and subsequently removed from the reaction mixture by devolatilization, the aryl silanes, especially, phenyl silane or benzylsilane, are more reactive under the present polymerization conditions, and accordingly are more efficient in forming long chain branches.
Preferred alkenyl substituted silane branching agents used herein include ethenylsilane, 3-butenylsilane, 5-hexenylsilane, vinycyclohexenylisilane, 7-octenylsilane, 17-octadecenylsilane 3-butenyl methylsilane, 7-octenyl ethylsilane, ethenyl n-butylsilane, 7-octenyl octadecylsilane, 3-butenyl phenylsilane and 7-octenyl benzylsilane. Mixtures of the foregoing silanes may also be used. Although the alkenyl silanes are preferably terminally unsaturated, alkenyl silanes containing internal unsaturated bonds, such as, 6-octenylsilane, can also be employed as long chain branching agents in the present invention. The alkenylsilanes employed to form the novel polymers of the present invention are obtained by the addition reaction of a diene, such as octadiene, to silane or a hydrocarbyl-substituted silane under conditions well known to those skilled in the art.
As used herein the term “long chain branching” refers to pendant oligomeric, hydrocarbyl groups attached to a polymeric chain, which groups have a carbon length of six or greater but are not the result of deliberately added comonomer polymerization, e.g., propene, 1-butene, 1-hexene, 1-octene, or branched olefin polymerization. Long chain branching in the present context includes polymer branches resulting from the reincorporation of remnants resulting from the &bgr;-hydride elimination process, with or without the involvement of the silane. Such long chain branches furthermore reflect the monomer diversity present in the polymerization reactor, since in effect, they are portions of preformed polymer which are reincorporated into a growing polymer chain.
Several techniques for measuring the extent of long chain branching in a copolymer already exist. Principle analytical techniques include those based on
13
C NMR analysis, optionally coupled with low angle laser light scattering or similar particle size measuring technique. Additionally, it is possible to arrive at an estimate of short chain branches, i.e., branches due to the C
3-8
comonomer remnant, by preparation of a control copolymer using a labled monomer, such as
13
C enriched 1-octene or ethylene, under the assumption that a similar level of branch distribution will exist in copolymers made under comparative conditions utilizing unmodified monomers. The level of longchain branching is thereafter determinded by subtraction. In the present technique, the level of long chain branching may additionally be quantified from a knowledge of the silane branching centers present in the resu
Campbell, Jr. Richard E.
Devore David D.
Peil Kevin P.
Timmers Francis J.
Lu Caixia
The Dow Chemical Company
Wu David W.
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